(1) Field of the Invention
The present invention relates to a process for laser beam hard coating of a ferrous metal substrate with diamond particles in a metal matrix. In particular, the present invention relates to hard coating a cast iron article, particularly a white iron casting, in order to improve the abrasion resistance of the coated surfaces of the article. More particularly the present invention relates to pumps having hard coated surfaces of the pump which are in contact with an abrasive water and tar sand mix.
(2) Description of the Related Art
The prior art has described processes for using nozzles providing a particle spray and a laser beam for applying a hard faced surface coating to a ferrous substrate. U.S. Pat. Nos. 4,724,299 to Hammeke and 6,316,744 to Nowotny et al are illustrative of the patent art. The disclosures of these patents are incorporated by reference herein in their entireties. In general, a powdered mixture of a metal alloy with particles of a hard material are coated on a substrate by melting the particles of the metal alloy on a spot surface of the substrate irradiated by the laser beam. Diamonds have been used in cutting tools as evidenced by U.S. Pat. Nos. 6,176,888 and 6,238,280 by unrelated processes.
Diamond particles have been incorporated into a metal alloy in the past in an attempt at providing a hard coating in parts which are continuously abraded by hard particles. The problem is that there is a poor bond between the diamond and the metal alloy when abraded by sand particles in an aqueous slurry. The result is that when abraded the diamond particles come loose from the coated surface. There is a need for an improved hard coating process and the resulting products. Relevant prior art is DE10024155 (which corresponds to EP1155768).